P1.2.4 Cannabinoid type 1 receptor antagonists

Central cannabinoid (CB1) receptors have recently been implicated in brain reward function, and are thought to have a role in controlling food consumption and in dependence and habituation. Repeated nicotine use may also over stimulate the endocannabinoid system and receptor antagonists may work by selectively blocking the CB1 receptors, thereby restoring the balance and inhibiting nicotine and food cravings. Rimonabant is the first selective cannabinoid type 1 receptor antagonist to have been produced and clinically tested, although is yet to be marketed in Australia. It was developed initially as a possible treatment for obesity, but it has also been proposed as an aid to smoking cessation and has potential to protect successful quitters from post-cessation weight gain, thereby addressing smokers’ reluctance to persist with a quit attempt because of concerns over weight gain. (Pomerleau et al., 2000) A Cochrane systematic review has assessed the effect of rimonabant compared to placebo in aiding smoking cessation. (Cahill and Ussher, 2007) In 2 trials suitable for inclusion in the review, rimonabant 20mg significantly increased the one-year cessation rate compared to placebo (n = 1049, OR 1.61, 95% CI 1.12 to 2.30, NNT = 18, 95% CI 10 to 87). Adverse events included nausea and upper respiratory tract infections, and weight gain was reported to be significantly lower among the rimonabant 20 mg quitters than in the placebo quitters. During treatment, overweight or obese smokers tended to lose weight, while normal weight smokers did not.